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Various techniques for stripping the insulation from very small (e.g., 30 μm diam) single-strand wires (made of copper—as in the case of magnet wire, phosphor bronze, manganin, etc.) without damaging them are discussed. Such approaches include the use of dissolutive chemicals, heat, short-wavelength laser radiation, and rotating friction wheels. A small handheld instrument that employs the last of these methods, and is capable of stripping wires with diameters ranging from 30 to 330 μm, has been developed and is described in detail.

Fermi-liquid theory (the standard model of metals) has been challenged by the discovery of anomalous properties in an increasingly large number of metals. The anomalies often occur near a quantum critical point--a continuous phase transition in the limit of absolute zero, typically between magnetically ordered and paramagnetic phases. Although not understood in detail, unusual behaviour in the vicinity of such quantum critical points was anticipated nearly three decades ago by theories going beyond the standard model. Here we report electrical resistivity measurements of the 3d metal MnSi, indicating an unexpected breakdown of the Fermi-liquid model--not in a narrow crossover region close to a quantum critical point where it is normally expected to fail, but over a wide region of the phase diagram near a first-order magnetic transition. In this regime, corrections to the Fermi-liquid model are expected to be small. The range in pressure, temperature and applied magnetic field over which we observe an anomalous temperature dependence of the electrical resistivity in MnSi is not consistent with the crossover behaviour widely seen in quantum critical systems. This may suggest the emergence of a well defined but enigmatic quantum phase of matter.

Arthropod fossils from Quaternary deposits in Greenland are considered. The few occurrences of Early and Middle Pleistocene age have yielded only three species of barnacles. This contrasts sharply with the last interglacial stage which is represented by many sites, from which a range of marine, lacustrine and terrestrial crustaceans and insects are reported. The only secure late glacial sediments from Greenland are found in the far south, and only a few taxa of arthropods have so far been identified from these. The best dated and richest faunas come from the Holocene. Most records of insects are from the late Holocene, but there are also a number of finds from the early and mid Holocene. Arthropods are considered good palaeoclimate indicators, because they are generally dispersed quicker, for example, than vascular plants. This group of animals is also highly useful for reconstructing former ecological conditions, because they occupy such a wide range of biotopes. A total of about 105 taxa have been reported so far, but several groups of arthropods, such as marine ostracodes, chironomids and oribatids, have received little attention, and many more taxa can be expected when these groups are being studied in the future.

A recent publication by the authors describes a spot welder which can be used to join small wires to samples of metallic materials. The article also discusses the selection of contact wires, the preparation of samples prior to welding, and other details of the welding method. In the present work, we give a much improved version of the power supply circuit, and offer additional information on the technique that was not discussed previously. A “universal” method of electropolishing is also described which may be used to remove oxides and other surface contaminants from samples prior to spot welding. This technique can be applied to a variety of materials, including rare earth elements and compounds, which are generally difficult to polish or etch using other chemical or electrochemical means.

A piston–cylinder cell has been constructed which makes it possible to achieve pressures of over 35 kbar at room temperature, and more than 29 kbar in a cryogenic environment. The use of a nonmagnetic cobalt–nickel alloy with an unusually high yield strength (1.97 GPa at 293 K) allows the cell to be used in the presence of large magnetic fields. It seems likely that the cobalt–nickel material can be used as a direct replacement for the celebrated (but largely unavailable) Russian nickel alloy in many applications where nonmagnetic pressure cells are needed. Such applications may also include other kinds of high pressure apparatus, such as diamond anvil and sapphire anvil cells. The pressure cell described in the present article employs the “Teflon cap” technique, and detailed information concerning the application of this method is given which can be used with a wide variety of cells of the piston–cylinder type.

In a conventional superconductor, the binding of electrons into the paired states that collectively carry the supercurrent is mediated by phonons — vibrations of the crystal lattice. Here we argue that, in the case of the heavy fermion superconductors CePd2Si2 and CeIn3, the charge carriers are bound together in pairs by magnetic spin–spin interactions. The existence of magnetically mediated superconductivity in these compounds could help shed light on the question of whether magnetic interactions are relevant for describing the superconducting and normal-state properties of other strongly correlated electron systems, perhaps including the high-temperature copper oxide superconductors.

A capacitive-discharge spot welder is described which is primarily intended for making electrical connections between small (

A growing number of metals have been found to show systematic deviations from the predictions of Landau Fermi-liquid theory. The most straightforward examples are magnetic metals in which the Curie ( T C ) or Neel ( T N ) temperature has been suppressed to 0 K by the application of hydrostatic pressure. Such systems are discussed here within a spin fluctuation framework which provides quantitatively accurate descriptions of the d-electron systems MnSi and ZrZn 2 near their ‘quantum critical points’, but which appears to be less successful (in its simplest form) in antiferromagnetic f-electron systems, particularly CePd 2 Si 2 , which at its critical pressure has a resistivity of the form Δρ ∝ T 1.2 = 0.1 over a temperature range extending from around 40 K to below 1 K. CeNi 2 Ge 2 , which is believed to be close to a quantum critical point at ambient pressure, shows similar behaviour. CeIn 3 , CePd 2 Si 2 and CeNi 2 Ge 2 exhibit superconductivity, in the first two cases limited to a narrow region near the critical pressure, making these the first unambiguous examples of magnetically mediated superconductivity.

Close to the border of antiferromagnetic order at high pressure the cubic stoichiometric compound CeIn 3 displays an unconventional normal-state resistivity followed by superconductivity at low temperatures. The superconducting transition temperature varies rapidly with pressure near the critical pressure where the Neel temperature collapses towards absolute zero.

The normal states of magnetic metals with vanishing Curie or Neel temperatures are investigated by means of measurements of the temperature and pressure dependence of the resistivity in the stoichiometric d and f compounds and . The results for the nearly ferromagnetic d metals may be described over a wide range in temperature and pressure in terms of a quantitative model of a marginal Fermi liquid based on dispersive spin-fluctuation spectra inferred from inelastic neutron scattering data. The behaviour of the antiferromagnetic f metals is also unconventional, but in a way which cannot yet be readily categorized. Near the critical pressure where , displays a resistivity of the form over nearly two decades in temperature before condensing into a short-coherence-length superconducting state below 0.4 K. The isoelectronic and isostructural compound , with a lattice cell volume slightly smaller than that of , remains normal down to 20 mK and shows a resistivity of the form over a decade below several kelvin at ambient pressure. These findings for the Ce systems have not yet been described consistently in terms of an extension of the model developed for the ferromagnetic d metals.

A clearance‐sealed piston pump has been developed which can be used to move high pressure gases in a closed loop for the purpose of purification, mixing, or phase equilibration. It has been designed primarily with the former role in mind, so that inert gases may be used in the preparation of high purity intermetallic compounds to suppress the evaporation of volatile constituents without introducing contamination. To this end, the device is made in such a way as to minimize outgassing, leakage, the formation of dead volumes, and the creation of debris. The pump is intended for use at pressures of up to 200 bar. Its structural materials are highly resistant to corrosion, and this should enable the device to be used with a wide variety of reactive gases. Flow rates of between 4.3 and 0.043 l min−1 can be sustained without difficulty using realistic loads, although larger and smaller ones are possible. The pump is capable of producing a head of 0.23 bar. A novel system has been developed for sensing and controlling the position of the piston. This makes it possible to monitor and vary the instantaneous flow rate while minimizing wear and vibration. The arrangement does not require the presence of a transducer or any kind of feedthrough in the clean, high pressure environment. It may find applications in other areas where positioning is needed under hostile or demanding conditions, such as inside ultrahigh vacuum apparatus.

A method is described for making electrical contacts to metallic materials which, because of their hardness and reactivity, can be very difficult to attach leads to using other techniques. These metals, including some of the heavy fermion materials, form inert and tightly bonded oxide layers which hinder the use of ordinary soldering methods. It has been found that a simple modification to an ordinary soldering iron, involving the replacement of the standard copper tip with one made of tungsten carbide, enables these oxide layers to be penetrated and electrical contact to be made without the use of flux. The size of the resulting contacts can be very small and their electrical resistance very low. Other, less viable, techniques for making contacts are also discussed, and a means of holding samples in place during soldering is described.

Recent studies of properties of heavy quasiparticles have helped to establish thatf electrons and conduction electrons in the normal states of certain U and Ce compounds are characterised by Fermi volumes consistent with Luttingeris Theorem and by integrated qnasiparticle masses which agree with measured linear coefficients of the specific heat. Evidence is presented that this Fermi Liquid picture may, however, break down when the ground state is near pressure or magnetic field induced phase transitions.

Annual reporting of inhibitors to factors (FVIII) and IX (FIX) to the Canadian Haemophilia Registry has suggested a lower prevalence than that published in the literature. We performed a prospective study to determine the prevalence of patients with inhibitors directed against either FVIII or FIX. Patients with inhibitors were classified as: (i) inhibitor test positive; (ii) inhibitor test negative but on immune tolerance induction (ITI); (iii) inhibitor test negative but bypass treatment recommended; or (iv) inhibitor resolved. One year later, the cohort was re-classified. The prevalence of inhibitors on 1 May, 2007 was 3.3% for haemophilia A, 0.6% for haemophilia B and 8.9% and 2.1% for severe haemophilia A and B. One year later 17 individuals gained and 11 individuals lost inhibitor status (10 of these with ITI). This study suggests that the prevalence of inhibitors in our population is lower than that was previously published. We hypothesize that this is primarily due to the increased use of ITI, but other factors may be the unselected nature of the cohort and the restriction of the study to one date thereby conforming as close as practical to the definition of prevalence rather than incidence. The classification system used in this study was easy for clinics to apply and was important in defining the population with inhibitors.

Introduction Mechanisms in general are a notorious source of reliability problems. This chapter deals with mechanical devices and systems (broadly construed) that are of particular concern in experimental work. The former include precision mechanisms, static and dynamic vacuum seals, and valves. A brief discussion of devices for preventing mechanical overtravel and overload is also included. Mechanical devices that are used under extreme conditions (e.g. in ultrahigh-vacuum and cryogenic environments) often suffer from friction and wear problems due to a lack of lubrication. A section of the chapter is devoted to lubricants (and especially dry lubricants and self-lubricating solids) that are useful under such conditions. Water-cooling systems are a common source of trouble in apparatus ranging from small-scale tabletop equipment (e.g. lasers) to large particle accelerators. Such problems include leaks, cooling-line blockages, corrosion, and condensation. These issues, and others, are discussed below. Mechanical vacuum pumps are dealt with in Chapter 7, while electrical connectors and cables (which are partly mechanical devices) are discussed in Chapter 12. Mechanical devices Overview of conditions that reduce reliability Some agents and environmental conditions that tend to diminish the reliability of mechanical parts and systems are as follows. (a) Particulate matter such as dust and grit can be very harmful to mechanical devices. It leads to accelerated wear and damage of moving parts (especially antifriction bearings, such as ball bearings), leaks in sealing devices, a decrease in the accuracy of precision mechanisms, and instabilities in mechanical assemblies requiring accurate registration of surfaces. (b) Moisture (including high humidity) causes corrosion and promotes biological growth (i.e. mold and fungi, which can release corrosive chemicals), degrades lubricants, and holds particulate matter that would otherwise escape on surfaces. […]

Covering many techniques widely used in research, this book will help researchers in the physical sciences and engineering solve troublesome - and potentially very time consuming - problems in their work. The book deals with technical difficulties that often arise unexpectedly during the use of various common experimental methods, as well as with human error. It provides preventive measures and solutions for such problems, thereby saving valuable time for researchers. Some of the topics covered are: sudden leaks in vacuum systems, electromagnetic interference in electronic instruments, vibrations in sensitive equipment, and bugs in computer software. The book also discusses mistakes in mathematical calculations, and pitfalls in designing and carrying out experiments. Each chapter contains a summary of its key points, to give a quick overview of important potential problems and their solutions in a given area.

Introduction Generally, nearly all of the equipment, devices, substances, and software that are employed in scientific research are of commercial origin. It is clear from everyday experience that the reliability and usability of such products can range from superb to abysmal. (Usability has an impact on overall reliability through its effect on human error.) Low-quality items, coupled with poor documentation (e.g. operating instructions), and lack of after-sales technical support from the companies that made them, can have a very harmful effect on laboratory productivity. The purpose of this chapter is to provide ways of avoiding such problems. Using established technology and designs As was pointed out in a general context on page 4, if reliability is important, one should not normally employ devices or software that use a technology which has not previously been in commercial production. Most innovative things have unforeseen problems (sometimes in very significant numbers), which can be found and dealt with only after such things have been tested by many users over an extended period. This is a particularly serious issue with computer software (see page 504).

Bleeding disorders are relatively uncommon, and most bleeding episodes occur as a result of local factors. Therefore a positive history of bleeding usually does not accurately predict the presence of a bleeding disorder. In a few cases the existence of certain patterns of bleeding, such as hemarthroses and petechiae, does allow an accurate prediction. On the other hand, the absence of bleeding following significant challenge is very helpful indeed in excluding a bleeding disorder. However, a negative history of bleeding in the absence of hemostatic challenge does not exclude a bleeding disorder. Accurate clinical analysis of suspected bleeding disorder requires acquaintance with the common causes of bleeding; these are described along with a clinical approach to diagnosis. The laboratory investigation starts with the performance of the “hemostasis screen”. A normal hemostasis screen excludes by far the majority of acquired defects, and further investigation, other than a repeat of the bleeding time, is rarely needed. When hereditary disorders are suspected, specific assay of individual factors, usually factors VIII (hemophilia A), IX (hemophilia B) and Von Willebrand factor, is advised. Recent advances in the understanding and the management of some disorders are described.

In the field of condensed matter physics, it is frequently necessary to produce motion at low temperatures. While this can often be done using a mechanical linkage which connects the cryogenic and ambient environments, space constraints sometimes render such a solution impractical. The following paper describes a miniature dc electric motor which can be used to produce motion under these conditions, and also presents a novel scheme for monitoring its position. The motor is a skew‐wound ironless device with a coaxial gearhead, and is capable of operating at a temperature of 4 K, in a vacuum, and in a magnetic field of several hundred gauss. The position monitoring arrangement requires no modifications to the motor or the addition of extra hardware, such as rotary encoders or potentiometers. Based on the angular dependence of the rotor inductance, it has been found to work with a number of different motors of the skew‐wound ironless type, both at room temperature and at 4°. Provisions have been made to allow the motor and position monitor to be operated by computer control. The author anticipates that they will find applications in other areas where motion is needed and space is at a premium.

We report on the observation of a superconducting phase in the itinerant electron ferromagnet UGe 2 . The superconductivity observed below 1 K and in a limited pressure range immediately below the critical pressure where ferromagnetism is abruptly suppressed, would seem to arise from the same electrons that produce band magnetism. This superconductivity is most naturally understood in terms of magnetic as opposed to lattice interactions and via a spin-triplet rather than a spin-singlet pairing normally associated with nearly anti-ferromagnetic metals.

Collections of adults ofParakiefferiella nigra Brundin indicate that this chironomid occurs widely in arctic and subarctic zones. In addition, it has occasionally been collected in cool temperate and boreal forest lakes of both North America and Europe. Although widely distributed, the larva and its habitat have not previously been described. Identity of the larva ofP. nigra has been established by studying associated reared specimens. The distinctive larva, with reduced second lateral mental teeth, is stenotopic, and on the basis of modern collections appears to be most abundant in cold, oligotrophic lakes. More data is required to establish the range of thermal environments inhabited by the larva. Larval head capsule remains ofP. nigra are common in late-glacial sediments of southwestern British Columbia lakes and provide important evidence for oligotrophic conditions during late-glacial time.

We have measured the temperature and field dependence of the resistivity of the unconventional superconductor Sr2RuO4 at pressures up to 3.3 GPa. Using the Shubnikov-de Haas effect, we find that the Fermi surface sheet believed to be primarily responsible for superconductivity becomes more two-dimensional with increasing pressure, a surprising result that is, however, consistent with a recent model of orbital-dependent superconductivity in this system. Many-body enhancements and the superconducting transition temperature all fall gradually with increasing pressure, contrary to previous suggestions of a ferromagnetic quantum critical point at approximately 3 GPa.

We have measured the temperature and field dependence of the resistivity of the unconventional superconductor Sr2RuO4 at pressures up to 3.3 GPa. Using the Shubnikov-de Haas effect, we find that the Fermi surface sheet believed to be primarily responsible for superconductivity becomes more two-dimensional with increasing pressure, a surprising result that is, however, consistent with a recent model of orbital-dependent superconductivity in this system. Many-body enhancements and the superconducting transition temperature all fall gradually with increasing pressure, contrary to previous suggestions of a ferromagnetic quantum critical point at approximately 3 GPa.

The absence of simple examples of superconductivity adjoining itinerant-electron ferromagnetism in the phase diagram has for many years cast doubt on the validity of conventional models of magnetically mediated superconductivity. On closer examination, however, very few systems have been studied in the extreme conditions of purity, proximity to the ferromagnetic state and very low temperatures required to test the theory definitively. Here we report the observation of superconductivity on the border of ferromagnetism in a pure system, UGe2, which is known to be qualitatively similar to the classic d-electron ferromagnets. The superconductivity that we observe below 1 K, in a limited pressure range on the border of ferromagnetism, seems to arise from the same electrons that produce band magnetism. In this case, superconductivity is most naturally understood in terms of magnetic as opposed to lattice interactions, and by a spin-triplet rather than the spin-singlet pairing normally associated with nearly antiferromagnetic metals.

Recombinant factor VIII concentrates are stable when administered in a reconstituted form according to the manufacturer's specifications, and undiluted via infusion with syringe mini-pumps. However many Haemophilia centres administer recombinant factor VIII further diluted in intravenous fluids for greater ease of administration. To investigate the stability of recombinant factor VIII during administration as a diluted infusion, reconstituted factor VIII was stored in polyvinylchloride (PVC) mini-bags undiluted (146 IU mL-1) and at factor VIII concentrations of 10 IU mL-1 and 2 IU mL-1. After 48 h of storage at room temperature in PVC mini-bags, the recoveries of factor VIII activity were 41.9% of the initial activity for the undiluted (146 IU mL-1) product and 43.7% of the initial activity for factor VIII diluted to 10 IU mL-1. For factor VIII diluted to 2 IU mL-1, the amount of factor VIII activity remaining at 48 h was only 1.8% of the initial activity. In contrast, 100% of factor VIII activity was recovered after 48 h when undiluted reconstituted product (146 IU mL-1) was stored in a syringe. To investigate the mechanism of factor VIII activity loss during storage, factor VIII samples collected after 0, 3 and 48 h of storage were analysed by immunoblotting with factor VIII antibodies. No evidence of factor VIII proteolytic degradation during storage was found, however, large amounts of factor VIII antigen were recovered from the empty PVC mini-bags following elution with denaturing detergent. We conclude that clinically significant losses of factor VIII activity occur during storage in PVC mini-bags and that the loss of activity is most likely due to protein adsorption onto the plastic surface. This loss of factor VIII activity during storage in PVC containers may substantially affect the safety and potential cost savings of administering recombinant factor VIII by continuous infusion.

To determine whether the factor V Leiden mutation is associated with decreased bleeding in individuals with severe hemophilia A, factor concentrate utilization, maximum annual number of bleeding episodes, and the prevalence of hemophilic arthropathy between carriers and non-carriers of the factor V Leiden mutation were compared. Heterozygosity for the factor V Leiden mutation was found in 6 of 137 subjects (4.4%). Carriers of the factor V Leiden mutation utilized less factor concentrate (geometric mean: 310 vs. 1185 units/kg/year) and had fewer bleeding episodes than non-carriers (proportion with 10 or fewer bleeding episodes in their worst year: 50 vs. 11%). However, the factor V Leiden mutation was not associated with the absence of arthropathy. The intron 22 inversion mutation of the factor VIII gene was tested for in a subgroup of 80 subjects, but it was not found to be a significant variable for any of the bleeding endpoints. The results of this small study are consistent with the hypothesis that the factor V Leiden mutation imparts a protective effect; however, a larger confirmatory study in which the factor VIII molecular defects can be controlled for is needed. Furthermore, most severe hemophiliacs who used fewer than 200 units/kg/year of factor concentrate or who had experienced 10 or fewer bleeding episodes per year did not carry the factor V Leiden mutation, suggesting that the proportion of severe hemophiliacs whose mild clinical course can be attributed to the factor V Leiden mutation is small.

The magnetic ordering temperature of some rare earth based heavy fermion compounds is strongly pressure-dependent and can be completely suppressed at a critical pressure, p$_c$, making way for novel correlated electron states close to this quantum critical point. We have studied the clean heavy fermion antiferromagnets CePd$_2$Si$_2$ and CeIn$_3$ in a series of resistivity measurements at high pressures up to 3.2 GPa and down to temperatures in the mK region. In both materials, superconductivity appears in a small window of a few tenths of a GPa on either side of p$_c$. We present detailed measurements of the superconducting and magnetic temperature-pressure phase diagram, which indicate that superconductivity in these materials is enhanced, rather than suppressed, by the closeness to magnetic order., Comment: 11 pages, including 9 figures

Lymphomatoid granulomatosis (LG) is an uncommon but potentially fatal disease. The disease primarily involves the lungs; however, skin, renal, and central nervous system (CNS) are seen in varying proportions. Neurological involvement occurs in one third of the patients, and confers a worse prognosis. The use of radiotherapy to treat CNS involvement in LG has not been well studied. We report a case of a 33-year-old man with multiple CNS lesions treated successfully with radiotherapy and review 6 other cases in the literature using similar treatment. These cases support the use of radiotherapy for CNS involvement in LG.

The life expectancy of individuals with haemophilia was close to that of the general population in the early 1980s. Since then, life expectancy has decreased, due to transfusion-transmitted virus infections. Deaths in individuals with haemophilia were investigated by analysing 2450 records from the Canadian Hemophilia Registry, for the years 1980-1995. Deaths were tabulated by age, year and cause, and compared with that of the Canadian male population by calculating standardized mortality ratios (SMRs). The median life expectancy at 1 year of age was calculated for various subpopulations and the impact of various population characteristics was assessed by survival regression modelling. There were 359 deaths and the annual number of deaths increased significantly after 1986. Risk factors were seropositivity to human immunodeficiency virus (relative risk 16.7, 95% CI 11.1-25.1), severe haemophilia (1.9, 1.3-2.7) and moderate haemophilia (1.8, 1.2-2.6). In HIV antibody negative individuals, the overall death rate was not increased (SMR 0.9, 95% CI 0.7-1.1) and only haemorrhage was significantly increased. In HIV antibody positive individuals, causes of death which were significantly increased were acquired immunodeficiency syndrome, liver failure, haemorrhage, lymphoma, liver cancer, nonspecific infections, and trauma or violence. Deaths due to the acquired immunodeficiency syndrome accounted for only 66% of the excess deaths in individuals who were HIV antibody positive. Life expectancy has markedly decreased since the onset of the HIV epidemic. The impact of HIV is underestimated by considering only deaths due to the acquired immunodeficiency syndrome; other HIV-linked causes need also to be considered.

The low-temperature resistivity of CeIn 3 has been measured at temperatures above the superconducting transition in the vicinity of the critical pressure (27.5 kbar) where the Neel temperature is suppressed to zero. With these measurements, it has been demonstrated that the resistivity exponent in CeIn 3 locks into a value of the order of 1.5 at low temperatures.

Metals on the border of magnetism have attracted great attention in recent times, as a number of them exhibit a superconducting phase at low temperatures in the vicinity of the critical pressure at which the magnetic transition temperature is suppressed to zero. We present a brief overview and comparison of the body centred tetragonal compounds CePd2Si2 and CeNi2Ge2, and the simple cubic CeIn3. In spite of the differences in structure and the detailed behaviour in the unconventional normal state near the critical pressure, these compounds share the existence of superconductivity at the border of antiferromagnetic order, and therefore are prime candidates for the study of a possible magnetic pairing mechanism. In this paper, we will solely present a comparison of the normal state properties of these materials.

Apparatus which can be used to demonstrate the Josephson effect is described. It is simple enough to be assembled in an afternoon and is dependable enough to use in a lecture demonstration. Using a few pieces of niobium wire, an oscilloscope and signal generator, a storage dewar of liquid helium, and some easily obtainable parts, it is possible to see many of the effects which have made Josephson junctions such interesting and useful devices. These include lossless currents (the dc Josephson effect), hysteresis, and macroscopic quantum interference. Phenomena arising from the production of microwave energy when voltages are applied across a Josephson junction (the ac Josephson effect) can also be observed.

Electrode erosion (especially anode erosion) is still an important problem for high‐power vortex stabilized arc lamps. A study of the electrode erosion mechanisms has therefore been carried out in vortex stabilized arcs operating at a maximum input power of 40 kW. It was found that three factors are important in the removal of electrode material: evaporation caused by thermal loading, ablation due to time varying stresses, and corrosion resulting from the presence of impurities in the gas. It was also found that the first two factors, and hence the erosion rates, can be affected significantly by the orientation of the electrodes and the presence of an external magnetic field.

A panel of commercially available monoclonal antibodies and five heteroantisera were used to distinguish and subtype 138 cases of acute leukemia (AL). The immunophenotype was compared with the French- American-British (FAB) classification obtained on the cases. The immunophenotype discriminated acute myelogenous leukemia (AML) from acute lymphoblastic leukemia (ALL) and recognized cases not distinguished by cytochemistry (22% of cases), mixed lineage phenotypes (13% of cases), and cases with separate populations of lymphoblasts and myeloblasts (one case). Using the immunologic panel and derived criteria to subtype AML, correspondence of the immunophenotype to the FAB subtypes M1, M2, M4, and M5 was possible in greater than 80% of cases. A combined classification of the immunophenotype and FAB morphology/cytochemistry was devised for AML subtyping. It is recommended that immunophenotyping should be done at least in all cases with negative orinconclusive cytochemistry. At present, we suggest that until a “gold standard” for identifying leukemic subtypes is developed, the best method for typing acute leukemia is by using a combination of morphology, cytochemistry and immunophenotyping.

The ac response at frequencies to 50 MHz of two thin‐film magnetic recording heads placed in mirror symmetry with respect to one another is measured as a function of relative position and applied dc fields. One driven head can be used to sense the presence of a second head even when the second head is not driven. An array of wires with current in alternating directions from wire to wire is used to obtain the absolute response of thin‐film heads. The efficiency of a head is found to be about 2/3.

Acute mixed myeloid-lymphoid leukemia is uncommon. We report four cases in which myeloid and lymphoid cell markers were observed simultaneously or sequentially when 94 patients with acute leukemia were phenotyped according to the French-American-British (FAB) classification system, with cytochemical stains, and with immunologically defined differentiation markers (identified by monoclonal antibodies and antiterminal deoxynucleotidyl transferase [TdT]). In one case, conversion from acute lymphoblastic leukemia to acute myeloid leukemia was noted (FAB L1, TdT+ to FAB M4, Auer rods, TdT-). In another patient, two distinct populations of myeloid and lymphoid blast cells were observed simultaneously (TdT-, LeuM1+/TdT+, LeuM1-). In two additional patients, acute leukemia was characterized by the expression of both lymphoid and myeloid markers on the same cell (TdT+/Leu M1+, B4+/Leu M1+ and greater than or equal to 70% TdT+, T11+, My9+). The Philadelphia (Ph1) chromosome was negative in all cases, though other chromosomal abnormalities were noted in three out of four cases. Malignant transformation of a pluripotential stem cell for both lymphoid and myeloid lineages, with or without the Ph1 chromosome marker, could explain the coexistence of distinct populations of lymphoblasts and myeloblasts in acute leukemia. Acute leukemia with a biphenotypic profile may reflect genome depression accompanying neoplasia.